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diff --git a/sys/imio/README b/sys/imio/README new file mode 100644 index 00000000..2e7228bf --- /dev/null +++ b/sys/imio/README @@ -0,0 +1,210 @@ +Image i/o. Coded May 1983, D. Tody. + +This initial implementation of IMIO, described in the ".hlp" design file, +provides most of the functionality of the IMIO interface, but is not +fully optimized internally. Features include: + + (1) 7 disk datatypes (ushort, silrdx). + (2) 6 in-core datatypes (the standard silrdx). + (3) Images of up to 7 dimensions are supported internally, though + only images of up to 3 dimensions are currently supported in the + interface. + (4) Fully automatic multidimensional buffer allocation, resizing, + and deallocation. + (5) Arbitrary number of input buffers, allocated in a round robin + fashion, need not be the same size or dimension. + (5) Fully automatic type conversion. + (6) General image sections, coordinate flip, and subsampling. + (7) Both "compressed" and "block aligned" storage modes are + supported, with IMIO automatically selecting the optimal + choice during image creation. The device blocksize is a + runtime variable. + + +Planned future improvements: + + (1) Boundary extension. + (3) Optimization to the get/put line procedures to work directly + out of the FIO buffers when possible. + (3) Addition of the get/put pixel procedures. + (4) The image header is currently a simple binary file (structure). + Only one image header structure per header file is permitted. + Will be modified to use database facilities, and to permit + embedded image headers. + (5) Support for the unsigned byte disk datatype. + + +FV NOTES: I've made the following bug fixes: + +In imioff: + The setting of IM_PHYSDIM was taken outside the loop called when + IM_NDIM was zero. There is was no way to set IM_PHYSDIM in the programmer + interface. + +In imhdr.h: + The offset to the user area IMU was changed from 603 to 613. This was + a typo? + +In impnln: + The coerce statement is wrong since imgobf calls coerce to the + appropriate data type. + +In impnln: + There was a typo which did not set ve. + +------------------------ + +Review image interface. Device namining convention, use of explicit +pathnames. File read/write permissions required. Why didn't imdopen +work. + +Remove imdmap.x from system library, put in libim.a. + + +Nov 84 + Optimized line at a time i/o. Added capability to reference directly +into the FIO buffer. This greatly improved the efficiency of simple image +operations (no section, type conversion, etc.), without reducing the generality +of the interface. + + +--------------------------------------------------------------------------- +IMIO Modifications, April 1985 + + +1. Boundary Extension + + types: constant, nearest, reflect, wrap + parameters: nbndrypix, tybndry, bndrypixval + + +2. Database Access + + New fields may be added to an image with IMADD. The value of an existing +field is set with one of the IMPUT procedures; automatic type conversion will +be performed if necessary and permissible. The value of an existing field is +fetched with an IMGET procedure. The image database interface is both forward +and backward compatible, i.e., no changes are required to current programs and +the same interface (ignoring minor semantic details) will be available when +image headers are moved into DBIO. + + +Functions + + get,g - get the value of a field + put,p - set the value of a field + add,a - add a new field to a database + acc - determine if the named field exists + del - delete a field + gftype - get field datatype + gfn - get field name (matching a template) + + +Procedures + + value = imget[bcsilrdx] (im, "field") + imgstr (im, "field", outstr, maxch) + imput[bcsilrdx] (im, "field", value) + impstr (im, "field", value) + imadd[bcsilrdx] (im, "field", def_value) + imastr (im, "field", def_value) + imaddf (im, "field", "datatype") + y/n = imaccf (im, "field") + imdelf (im, "field") + type = imgftype (im, "field") + + list = imofnl[us] (im, template) + nchars/EOF = imgnfn (list, outstr, maxch) + imcfnl (list) + + +The database interface may be used to access any field of the image header, +including the following standard fields. Note that the nomenclature has +been changed slightly to make it more consistent with FITS. Additional +standard fields will be defined in the future. + + + keyword type description + + i_naxis i number of axes (dimensionality) + i_naxis[1-7] l length of an axis ("i_naxis1", etc.) + i_pixtype i pixel datatype (SPP integer code) + i_minpixval r minimum pixel value + i_maxpixval r maximum pixel value + i_ctime l time of image creation + i_mtime l time of last modify + i_limtime l time when limits (minmax) were last updated + i_title s title string + + +The following additional field names are recognized, but may disappear in the +future: + + i_history s history record (a string buffer at present) + i_pixfile s pathname of the pixel storage file + + +The names of the standard fields share an "i_" prefix to reduce the possibility +of collisions with data dependent keywords, to identify the standard fields in +sorted listings, to allow use of pattern matching to discriminate between the +standard fields and user fields, and so on. The use of the "i_" prefix is +made optional for the convenience of the interactive user, but the full name +should always be used in compiled programs. + + +3. Subfile Management (not implemented) + + A subfile B of file A is a file which is logically subordinate to A but +which is physically a separate file to the host operating system. A subfile +need not reside in the same directory as the main file. + +FIO shall provide support for subfiles as an abstract datatype. For each +ordinary file there shall optionally be zero or one subfile index files with +the same root name as the main file but with the extension .zsf. The index +file, if present, shall list the subfiles of the main file. The operations +supported by FIO for subfiles shall include the following: + + + add a subfile to index and return pathname + delete a subfile from index and return pathname + get the pathname of a subfile + delete both index entry and physical file + delete a file and all subfiles + + +It is important that FIO maintain the mapping of a subfile name to a physical +file name to permit moves, copies, renames, etc. of files and their subfiles. +Having to open the index file to get the pathname of a subfile is however +inefficient. To achieve both flexibility and efficiency the system packages +IMIO and DBIO will cache the names of subfiles to eliminate most accesses to +the index files. + + + add a subfile: + add subfile to the index + cache pathname + + open subfile: + repeat { + open subfile using cached pathname + if (file cannot be opened) { + call fio to get the pathname of the subfile + if (different from cached pathname) { + update cached pathname + next + } else + error: cannot open file + } else { + read file header and verify that this is our subfile + if (not our subfile) { + close file + call fio to get the pathname of the subfile + if (different from cached pathname) { + update cached pathname + next + } else + error: not our subfile + } else + break # success + } + } |